DTDC Courier & Cargo — Insurance claim refund from DTDC

I have done a courier from Hyderabad to bangalore consign no: D20209414. I have insured the items for 2lacs and the premium amount comes to somewhere around 8k. But I wanted to change the insurance amount to 50k only now. So I am claiming a refund of 6k.
I have already contacted the booking person and he is not picking up the call and neither available in the office. Need the response for this issue at the earliest.